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1708116 
Journal Article 
Sodium sulfate decomposition in dry atmospheres 
Samadhi, TW; Elliott, JC; Jones, LE; Clare, AG 
2001 
74 
3 
47-56 
WOS:000168406300001 
Na2SO4 in silicate glass batches is an environmental issue, since it releases SO2 upon decomposition. Decomposition of Na,S04 in different environments is studied by mass-loss measurements combined with evolved gas analysis, and thermochemical modeling. The decomposition experiments are undertaken in dry, pure O-2(S), Ar(g), N-2(g), and air(g) at 95 kPa total pressure. Thermochemical calculations using the code F*A*C*T predict SO2(g), Na(g), Na2SO4(g), NaO(g), and, in some cases. NO(g) as major emission species, The concentrations of these species increase with temperature. Na2SO4 decomposition initiates at approximate to 1373 K. Isothermal decomposition exhibits linear behavior with respect to time in 1473 to 1673 K range. At 1673 K, the decomposition rate is 24 . 10(-4) mg/(mm(2) min) in UHP (ultra-high purity) O-2 and 69 10(-4) mg/(mm(2) min) in UHP N-2. Evolved gas analyses identify SO(g)/SO2(g) as the emitted pollutants. In O-2-rich atmospheres, SO(g) is a significant product as well as SO2(g). In inert atmospheres. SO2(g) is the sole decomposition product. At 1673 K in UHP O-2. the concentration is 55 ppm (by volume) for SO(g) and 61 ppm for SO2. At 1673 K in UHP N-2 SO2(g) concentration is 651 ppm. The decomposition is described by a surface reaction mechanism. in which SO2 is generated by surface rearrangement of sulfur-oxygen complexes on the Na2SO4 melt surface. Inert atmospheres increase SO2 emission by facilitating this rearrangement process. O-2-rich atmospheres passivate the melt surface, which favors the emission of lighter molecules such as SO(g).